Django Extend AbstractUser and use email Field as default in other field

I'm using Django 1.9.2 with python 2.7.3, rest framework and allauth. I'm extending from django.contrib.auth.models.AbstractUser and I want to get the email field from AbstractUser and use it as default in other field:

Thanks to RA123 for the orientation, I have also overwritten the save method of MyUser and instead of implementing my own UserManager, I have implemented the default and I have added the necessary fields: